Containers provided with bungs, namely bung-type barrels and drums, are customarily made from sheet steel and can be used for the transportation or storage of a wide variety of solid and liquid materials which may be flowable to enable them to be introduced into or discharged from the drum through the opening provided when the bung is unstoppered. In many cases, the steel sheet forming the container must be protected against corrosion by water or other aggressive corrosive materials which may be introduced into the container by a suitable internal coating. Bung-type drums which are internally lacquered are frequently used for this purpose although internal coatings of other materials which are more resistant to aggressive and corrosive substances than conventional lacquer may also be employed.
While in some cases the drum or barrel is destroyed after use by compaction or scrapping, it is frequently required to reuse the barrel or drum for the transport and/or storage of, for instance, another substance. In such cases, not only is it necessary to free the barrel or drum from all residues of the substance previously transported and thus to empty the container as fully and completely as possible, but it also is required to clean the interior of the container before introducing the new substance.
For water soluble substances it generally suffices to rinse the interior of the barrel or drum with water. A problem with this, of course, is that the rinsing water must be discharged and frequently is contaminated so that it might pose an environmental hazard. With substances that are not as readily soluble, the cleaning can be effected with hot water to which detergents or other cleaning agents can be added. There are, however, substances requiring transportation and storage in drums or barrels whose residues cannot be readily removed in either of the aforedescribed ways so that intensive cleaning is required. The intensive cleaning generally involves a high degree of heating of the barrel or drum to the point that sealing materials which may be incorporated in the folds or bung structure of the barrel may decompose or so deteriorate that the barrel or drum becomes useless. Furthermore, the heating must be carried out in relatively expensive units, for example, furnaces, ovens or the like.
It has been suggested to cover the interiors of containers with foils. These systems also require cleaning and frequently heating so that the foils may be destroyed or damaged like the sealing compositions and sealing rings as described previously. As a consequence, cleaning processes are not desirable when such foil linings are used. Finally, when washing liquids are employed it frequently is found that they introduce problems and promote damage to the linings and seals of the barrel or drum during heating.